Phenothiazine-modified electrodes: a useful platform for protein adsorption study.

Area of Science:

• Electrochemistry
• Biosensors
• Protein Adsorption

Background:

• Phenothiazine derivatives like thionine chloride (TC) can be immobilized on indium-doped tin oxide (ITO) electrodes.
• Immobilized phenothiazines exhibit fluorescence and strong binding affinities for proteins.
• Understanding protein adsorption on modified electrodes is crucial for developing biosensors.

Purpose of the Study:

• To investigate the adsorption of glucose oxidase (GOx) on phenothiazine-modified electrodes.
• To assess the potential of these electrodes for biochemical applications, including protein quantification and glucose sensing.

Main Methods:

• Fabrication of ITO electrodes modified with phenothiazines (thionine chloride and analogues) via diazotization-reduction or oxidative polymerization.
• Characterization of protein adsorption using fluorescence quenching, conductive-mode atomic force microscopy (CM-AFM), and electrochemical impedance spectroscopy (EIS) with Fe(CN)6(3-/4-).
• Kinetic analysis of GOx interaction with immobilized TC and assessment of electrode performance as glucose sensors.

Main Results:

• Phenothiazine-modified electrodes showed stable GOx adsorption at pH > 5, with emission decay upon protein injection.
• GOx adsorption followed pseudo-first-order kinetics, with maximum rates at pH > 5 and increased adsorption with higher protein concentration.
• Adsorbed GOx increased charge-transfer resistance (RCT), indicating stable immobilization and enabling glucose detection (1-60 mM) with reproducible responses.

Conclusions:

• Phenothiazine-modified electrodes provide a robust platform for studying protein adsorption and developing biosensors.
• The electrodes maintain GOx bioactivity, allowing for sensitive and reproducible glucose quantification.
• These modified electrodes are valuable tools for protein quantitation and understanding protein-surface interactions.